waterhemp in field

3 Ways to Protect Soybeans from Palmer Amaranth and Waterhemp

April 12, 2022 7:00 a.m.

By Valent

The 2022 season is shaping up to bring challenges to protect soybean that growers haven’t faced in many years. Supply chain constraints are putting pressure on many weed control products, such as glyphosate and glufosinate and with higher fertilizer costs, it is becoming more common to find growers considering back-to-back soybeans.

For growers in this situation, having a strong herbicide strategy going into the season will be critical to getting the most out of their crop and building a solid foundation for the future.

Consider these strategies:


If you don’t have your weed management plan ready, now is the time. And if you don’t have residual herbicides in your plan for the year, it’s also time to take a hard look at that decision. Residual herbicides provide a window of protection – helping shield your crop from weed pressure in those tough weather conditions that can limit getting into the field. It’s risky to assume you will be able to manage weeds with multiple sprays through the season in any year, and especially so given the current market. Starting with a foundation herbicide that has multiple effective modes of action and six to eight weeks’ residual control of troublesome weeds, such as Palmer and waterhemp, is wise. Those pair well with an overlapping residual herbicide to get the crop to canopy for season-long weed control.

“Programs that utilize strong foundation herbicides, followed by post-applied overlapping residuals, minimize the risk of bad weather and field conditions giving weeds a leg up on your soybean crop,” said John Pawlak, product development manager for Valent U.S.A. “An integrated weed control program is key to meeting sustainability goals in the field, and post-applied residual herbicides like Perpetuo are important tools in the battle to protect crop yields and soil resources from weed pressure.”

Setting a weed management plan that includes residuals with multiple modes of action you can rely on, especially where you are looking to control tough weeds like Palmer amaranth and waterhemp, is a commitment to the success of your crop. You know signs of weed escapes and resistance spell trouble for the future, and an unchecked seed bank only makes the next year’s crop a bigger battle.

Residual herbicides give the added benefit of killing weed seedlings at germination without requiring additional passes across the field. Your strongest play is an approach with overlapping pre- and postemergence residual herbicides that can tackle the long germination windows of troublesome weeds throughout the growing season.


Gambling that the supply chain is going to improve before the season is just that, a gamble. Waiting until your application window to purchase your herbicide or to evaluate alternative products is a recipe for frustration at minimum, and could result in fields being left untreated, depending on the situation facing retailers and custom applicators as we get into the growing season. Lock your herbicide position in early and take that additional risk out of the equation.

Evaluating options beyond your go-to herbicide regimen, or even building your Plan B for the season, likely means additional research. As you consider new or alternative products, make sure they are effective against the weed pressure you face and your preferred production methods. While limited availability of some products might be offset with tillage or cultivation, the effect of these practices on your soil health efforts may make that a non-starter. Premix options, especially those offering burndown and residual control, can fill multiple roles in a weed management plan and help meet your goals for the year.


Inputs are typically among the biggest investments into a crop, and this year will be no different. Tight supplies, fuel costs and transportation challenges mean every product has to work. If you’re using a product for the first time or have limited experience, resist the urge to rely solely on others’ expertise or skim through the materials. Taking the time to really dig into your plan prior to getting into the field can help you adapt most effectively to changing conditions when fieldwork begins.

Once your plan is set and your position secured, execution comes front-and-center. This is where knowing your products, equipment and fields helps you make the most of your crop inputs, as well as your time. Be ready to take advantage of narrow windows to get across the field for application by knowing your spray equipment, including nozzles and rates, your adjuvants and optimal spray volumes.

Whether you’re using a new herbicide or familiar products, know what timing is likely to see the best results and how they impact the rest of your operations. And if your plan doesn’t include residuals, how will you address delays in field work or limits on passes? Do you have a priority list of your fields to ensure weed pressure is being addressed strategically if a tight application window means not every acre gets covered? Does your plan consider your soil conservation practices and next year’s crop rotation?

“When looking at products with an overlapping residual, Perpetuo® has the advantage of flexibility - allowing for a cover crop to be planted after harvest and with rotational intervals allowing for a wide variety of crops to be planted the following year,” Pawlak says. “It also has the long window to help get your crop to canopy, all of which helps meet your sustainability goals with or without conservation tillage.”

Whether you’re making the most of trusted herbicides or trying a new mix this season, taking the time to understand how each product works will help maximize your return on your investment. Be mindful of weed growth stages and aim to target smaller weeds with lower rates, as opposed to needing to use higher rates on larger weeds. Tank mix compatibility is also an important consideration, as some products lose efficacy or create undesirable reactions if exposed to certain adjuvants, herbicides, fungicides, insecticides, biologicals or fertilizers in the sprayer. Likewise, your sprayer settings – from nozzle patterns to volume and droplet size – can have significant effects in the field.

Ultimately, success at harvest is built on solid preparation and execution throughout the growing season. As you prepare your weed management plan, consider including a premix herbicide delivering both burndown control of emerged weeds and residual weed control for postemergence. Perpetuo™ Herbicide from Valent U.S.A. hits that mark with proven chemistries for resistant Palmer amaranth, waterhemp and additional small-seeded broadleaves and grasses. To learn more about Perpetuo, download the Herbicides for Soybeans eBook and visit Valent.com or contact your local retailer.